Carbon canister storage systems are known for storing fuel vapors emitted from an automotive-type fuel tank or carburetor float bowl or other similar fuel reservoir to prevent emissions of fuel vapors into the atmosphere. These systems usually consist of a canister containing carbon or other medium which will releasably adsorb the fuel vapors. The canister would have an inlet from the fuel tank or other source of fuel vapors, the fuel vapors flowing typically under slight pressure into the canister to be adsorbed and stored by the filter medium therein. The canister also typically would have a fresh air inlet and a purge line connected to the engine intake manifold. During operation of the engine, vacuum in the intake manifold would draw air through the canister to the engine, thereby desorbing the filter medium of the fuel vapors.
Fuel vapor emission control canisters generally and their use in controlling emissions of fuel vapors from motor vehicles are well known to the skilled of the art. Such canisters, in addition to housing a bed of an adsorbent material, often provide other filtering means. Exemplary of such technology is that taught in U.S. Pat. No. 4,568,797 to Brand; U.S. Pat. No. 4,454,849 to Mizuno et al; and U.S. Pat. No. 4,326,489 to Heitert.
In U.S. Pat. No. 3,683,597 to Beveridge et al an activated charcoal canister assembly 16 is shown for controlling loss of fuel vapor from a vehicle fuel tank. The canister assembly comprises a molded body 16 having an upper end wall characterized by an annular outer portion 28 provided with flat ribs 32 which extend radially to a sealing lip 31. A cover member 40 is secured to a cylindrical inner wall 30. Chamber 45 within molded body 16 contains charcoal 46 retained by lower closure member 47 and screen 48. Wave spring 49 provides an upward bias against lower closure member 47. The lower closure member has a grid structure, including radial ribs 56. Additional canister configurations disclosed by Beveridge et al include compressed polyurethane pads to retain adsorbing material within the canister tightly packed. The Beveridge et al devices do not lend themselves as readily as is desirable to automatic assembly operations. In U.S. Pat. No. 3,728,846 to Nilsson a fuel vapor recovery system is shown comprising a filter connected by a vent line to the fuel tank. The filter is located in the engine compartment and the vent line is "lead through the upper portion of the vehicle body." The filter 6 comprises an open canister 19, the bottom of which is provided with a plurality of perforations 20 and serves as an air intake. Within the canister there is, at the bottom, an air filter element 21 and above this a filter portion 22 consisting of a filter element 23. The top and bottom of filter element 23 are bordered by a thin layer 24 of air pervious material, such as foamed plastic. Placed outside the layers 24 are filter element bottoms 25 that are perforated, have a certain rigidity and are intended to hold the filter portion 22 together. The filter element 23 is said to consist of active carbon grains. The canister 19 is sealed by a lid 26. A first hole 27 through the upper lid is connected to the vent line from the fuel tank. A second hole 28 is connected to the motor's air intake system. An apparently rigid and fixed central collar 29 extends inwardly from lid 26 to bear against the upper filter element bottom 25 to fix the position of the filter portion 22 within the canister. In U.S. Pat. No. RE 26, 196 to Hall a cylindrical evaporative emission canister for a motor vehicle has a filter 27 open to the atmosphere at one end through a screen 29. A vent line 13 from the opposite end of the canister is connected to a fuel tank 11. A duct 22 leads from the engine air cleaner 16 to an electrically driven, heat actuated air pump 23. Air pump 23 operates when the engine 10 is both off and hot. Discharge line 26 from the air pump 23 leads to the filter 27 containing suitable adsorbent material 28 such as charcoal. A conduit 30 from the filter 27 leads to a thermal cleaning device 31 which is connected by an air duct 32 to the carburetor 15. All vent lines (line 13 from fuel tank to filter, line 26/22 from air cleaner to filter, and line 32/30 from carburetor to filter) extend into the filter 27 and there are in fluid communication with each other. In U.S. Pat. No. 3,854,911 to Walker an arrangement is shown for controlling evaporation from a carburetor float bowl of an engine and from an associated pressurized fuel tank. Vapors are vented to a vapor absorbing canister 21. In U.S. Pat. No. 4,058,380 to King an evaporative emission control system having a bed of activated carbon is provided with one or more baffles to route the vapors therethrough to improve efficiency of emission control. In U.S. Pat. No. 4,203,401 to Kingsley et al an evaporative emission control canister has a cylindrical canister housing, a closed lower end wall, an upper end wall and a cylindrical inner wall depending from the upper end wall. An air-vapor permeable support means is positioned within the housing above the lower end wall in abutment against the lower free end of the cylindrical inner wall. This defines, with the lower end wall, an air chamber in fluid communication with the atmosphere. It also defines, within the canister, an outer canister chamber and an inner canister chamber. The inner canister chamber is connected by a fuel bowl vent valve to the float bowl of an engine to receive vapors from the float bowl when the engine is not in operation. The outer canister chamber is connected to receive vapors emitted from the fuel tank. Both the inner and outer chamber within the canister are connected to the vapor purge chamber of a vapor purge control valve, whereby fuel vapors can be purged from the canister assembly to the engine during engine operation. In U.S. Pat. No. 4,306,894 to Fukami et al a canister for a fuel evaporative emission control system of an engine contains adsorbent divided into at least two layers by a pair of spaced filter plates, so that fuel vapors can be defused into all parts of the adsorbent layers under the action of the filter plates and the hollow space between them. In U.S. Pat. No. 4,326,489 to Heitert a fuel evaporative loss control system comprise a canister 22 containing carbon and having a purge line leading to an engine intake manifold. A purge control valve meters the purged fuel vapors into the engine in an amount proportionate to the rate of air flow to the engine. The interior of the shell 30 of canister 22 is partitioned into two end chambers 40 and 42 by a pair of annular steel perforated screen plates 44 and 46, respectively. The space between the screens being filled with activated charcoal or other suitable vapor adsorbent 23. A spring 50 located between screen 44 and the cover 32 of the canister biases the upper screen against the adsorbent. In U.S. Pat. No. 4,454,849 to Mizuno et al a canister for a fuel vapor emission control comprises a fuel vapor guiding pipe 16 which extends into a bed of adsorbent material within the canister housing, and a deflector 17 within the adsorbent for deflecting the flow of fuel vapors and thereby dispersing them throughout the bed. Finally, in U.S. Pat. No. 4,658,797 to Brand a ventilation device for the fuel tank of a motor vehicle, includes a ventilation line 3 connecting the tank with the atmosphere through a fuel vapor filter 4. The filter 4 also is connected to the intake system 6 of the vehicle engine 1 by means of a filter exhaust line 5. A valve 7 in line 5 is closed when the engine is off to prevent the collection of fuel vapors in the intake system.